I had the two files paired, however, I lost what contained the reverse reads. Is there any way to redo this lost file using only file 1 (foward)? Sorry for ignorance, I'm new to this area. I need the file to do the metagenomic assembly using Spades (metaspades), which needs these 2 files (forward and reverse).

By "lost" you mean you deleted the file with R2 (reverse) reads? If so, no, you can't recover this data, it is gone forever. You will have to assemble the genome using the R1 as single-end reads, with the parameter -s file_R1.fastq.

But if by "lost" you mean you converted your R1 and R2 files into an interleaved fastq file, then you can feed SPAdes with this file, using the parameter --12 file_interleaved.fastq.

If you deleted the file, you can try to contact the sequencing provider and ask if they still have the files stored.

edit: Actually, it seems metaSPAdes does not support single reads, see genomax comment bellow. You may try to use it, but I am not certain it will work. You may contact the developers and ask about this, they are really responsive.

I lost what contained the reverse reads. Is there any way to redo
this lost file using only file 1 (foward)?

If lost refers to permanent loss of data (e.g. deletion/corruption of the file) then there is nothing you can do to recreate the file. You will need to ask your sequence provider to provide you with a new copy.